1. Field of the Invention
The present invention relates to an independent device for draining the power from Nickel Cadmium batteries so they may be recharged to a useful condition. The "deep cycler" is designed to drain batteries of 15 volts or less and thus prevent or eliminate the "memory set" that eventually occurs in most rechargeable nickel cadmium batteries.
The device is designed to be clipped onto a battery for purposes of draining current from the battery prior to recharging the battery. It uses two circuits. They are separately actuated by a relay according to the voltage level of the battery. The first circuit provides an initial high-voltage current drain that is greater than the current drain of the second circuit, and it includes a voltage monitoring circuit that uses LEDs biased at different voltages. The second circuit provides a final current drain after the initial current drain of the first circuit, and it uses an incandescent lamp to indicate discharge until the battery voltage drops to 0.7 volts. A voltmeter may be inserted into V+ and V- voltmeter receptacles for further monitoring of the battery voltage.
2. Description of Prior Art
Existing technology for draining power from Nickel Cadmium batteries has been limited to voltage specific drains, for example a 9 volt discharger. This device is unique in that it is designed to discharge or "deep cycle" any battery with a voltage level below 15 volts.
U.S. Pat. No. 4,829,225, Rapid Battery Charger, Discharger and Conditioner is intended to condition and charge batteries of only a specific voltage and requires an external power source.
U.S. Pat. Nos. 4,829,007 and 4,829,225 use a method of "pulsing" Nickel Cadmium batteries to discharge a specific level voltage. Again these devices are limited to one voltage and require external power. They also incorporate a charging device and are thus more restrictive in use to one specific designed battery.
U.S. Pat. No. 5,107,196, "Battery Bug" is similar to the applicants device in that it does not use external power and is designed only to drain a battery and uses LEDs as voltage indicators. However, there are several major differences in the design and effectiveness of this unit. They include:
1. The "Battery Bugs" two circuits do not appear to be separated, but are instead installed in constant parallel to each other. This design allows a battery to drain too quickly at high voltages and too slowly at low voltage. Too fast drain can damage the battery cells. PA1 2. The use of LEDs for monitoring is good only to approximately 1.5 volts, below that value the LEDs do not illuminate.
The applicant's device uses LED circuits biased at specific voltages above 3.3 volts, and an incandescent lamp of specific value to indicate voltage discharge to 0.7 volts. In addition the applicant's device varies the circuit resistance from 3.3 ohms to a 1 ohm "cold" final resistance. This 1 ohm circuit is the desired design resistance for deep cycling NiCad batteries.
In addition, the applicant's device permits the battery to be relieved of its load by opening S1, thus allowing any residual battery energy to be indicated through the LED, thus showing the battery in not fully deep cycled.